Improving Performance of III-V Solar Cells Grown on Spalled Germanium with Ex Situ Substrate Planarization

John Mangum, Anna Braun, Allison Perna, John Geisz, Aaron Ptak, Corinne Packard, Ryan France

Research output: Contribution to conferencePaper


Controlled spalling allows removal of devices and provides an opportunity for cost reduction through substrate reuse. However, the fracture-based process can leave behind morphological surface features, notably river lines, that can disrupt epitaxial growth and degrade device performance. We investigate the viability of various wet etch chemistries to planarize river lines to ensure high-quality device growth and performance without mechanical repolishing, and so maintain a route towards cost-effective reuse. Etching in a HF: HNO 3 :CH 3 COOH solution effectively planarizes river lines and produces a surface that yields devices with equivalent performance to those grown on epi-ready Ge wafer surfaces. Further studies will focus on optimizing etch composition, temperature, and time to minimize material removal while maintaining a suitable surface for high-quality epitaxy.
Original languageAmerican English
Number of pages4
StatePublished - 2023
Event2023 IEEE 50th Photovoltaic Specialists Conference (PVSC) - San Juan, Puerto Rico
Duration: 11 Jun 202316 Jun 2023


Conference2023 IEEE 50th Photovoltaic Specialists Conference (PVSC)
CitySan Juan, Puerto Rico

NREL Publication Number

  • NREL/CP-5K00-88876


  • germanium
  • performance evaluation
  • photovoltaic cells
  • photovoltaic systems
  • planarization
  • rivers
  • surface morphology


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